Immunization and Vaccine-Preventable Diseases Practice Questions

Q: Immunization with Rotavirus should be completed by what age?

12 months. ### Explanation **Correct Answer: C. 12 months** In the context of the **National Immunization Schedule (NIS)** in India, the Rotavirus vaccine (RVV) is administered in a 3-dose schedule at **6, 10, and 14 weeks** of age. The critical programmatic guideline is that the vaccination series **must be completed by 12 months of age**. If a child misses the scheduled doses, the vaccine should not be initiated or continued beyond the first birthday. The medical rationale for this age limit is based on the natural epidemiology of rotavirus infection and safety concerns. Most severe rotavirus-induced dehydration occurs in early infancy; by the time a child is older than one year, they have likely acquired natural immunity through subclinical exposure, reducing the benefit-to-risk ratio of the vaccine. **Analysis of Incorrect Options:** * **A & B (2 and 3 months):** These represent the ages when the first and second doses are typically administered (6 and 10 weeks). While the primary series starts here, the "completion" window extends much further. * **D (18 months):** This is incorrect as the risk of **intussusception** (a rare but serious side effect) was historically thought to increase if the vaccine was administered to older infants. Current NIS guidelines strictly cap the administration at 1 year. **High-Yield Clinical Pearls for NEET-PG:** * **Route & Dosage:** RVV is given **orally**. The dosage depends on the specific brand (e.g., **Rotavac** is 5 drops; **Rotasiil** is 2.5 ml). * **Type of Vaccine:** It is a **Live Attenuated** vaccine. * **Storage:** It is highly heat-sensitive and should be stored at **+2°C to +8°C**. * **VVM:** Rotavirus vaccine vials in India now come with Vaccine Vial Monitors (VVM) on the cap. * **Catch-up:** If a dose is missed, it can be given at any time before 12 months, maintaining a minimum 4-week interval between doses.

Q: An 11-month-old child presents for vaccination. He has previously received Polio vaccine and BCG. What vaccines should be administered at this visit?

Measles, DPT, OPV, Hib, Hepatitis B. ### Explanation The core concept tested here is the **National Immunization Schedule (NIS)** of India and the management of a **"partially immunized"** child. **1. Why Option B is Correct:** The child is 11 months old and has only received BCG and Polio (likely OPV 0 at birth). According to the NIS, the primary series of **Pentavalent (DPT + Hep B + Hib)** and **OPV** (3 doses) should have been completed at 6, 10, and 14 weeks. Since the child missed these, they must be administered now as "catch-up" vaccination. Additionally, the first dose of **Measles (MR-1)** is scheduled at 9 completed months. Therefore, at 11 months, the child is eligible for all these antigens simultaneously. **2. Analysis of Incorrect Options:** * **Option A:** BCG is already given; repeating it is unnecessary. * **Option C & D:** These options omit **Measles**, which is the most critical vaccine to be administered between 9–12 months of age. Option D also misses **Hib**, which is now integrated into the Pentavalent vaccine in the NIS. **3. High-Yield Clinical Pearls for NEET-PG:** * **Pentavalent Vaccine:** Replaced individual DPT, Hep B, and Hib doses. It is given IM in the anterolateral aspect of the mid-thigh. * **Measles/MR Vaccine:** Administered Subcutaneously (SC) in the right upper arm. * **Catch-up Rule:** Under the NIS, DPT and Hep B can be given up to 7 years and 1 year of age, respectively. However, Pentavalent is generally given up to 1 year. * **Vitamin A:** Don't forget that the 1st dose of Vitamin A (1 lakh IU) is administered orally along with the 1st dose of Measles at 9 months. * **Open Vial Policy:** Applies to DPT, Hep B, OPV, and Pentavalent; it does **not** apply to Measles or BCG (must be discarded after 4 hours).

Q: An OPV vial shows a Vaccine Vial Monitor (VVM) in which the inner square is lighter than the outer circle. What does this symbol indicate?

Use the vaccine if the expiry date has not been reached. ***Use the vaccine if the expiry date has not been reached*** - The **Vaccine Vial Monitor (VVM)** symbol on OPV vials changes color based on cumulative heat exposure, with the inner square remaining lighter than the outer circle in stages 1-2, indicating the vaccine is still potent. - When the VVM shows the inner square **lighter than the outer circle** and the **expiry date has not passed**, the vaccine may be used as it maintains its efficacy. The vaccine may be used only if the VVM remains at the usable stage and the printed expiry date has not passed. *The vaccine has reached its expiry date* - The VVM symbol indicates **heat exposure status**, not expiry date - the actual expiry date is printed separately on the vial label. - A VVM can show **stage 1-2 (usable)** even when the expiry date has passed, but expiry date takes precedence in decision-making. *The vaccine has not been stored properly* - Improper storage would cause the VVM to progress to **stage 3-4** where the inner square becomes **equal to or darker** than the outer circle. - A usable VVM (inner square lighter than outer circle) indicates that the cumulative heat-discard point has not been reached; it does not confirm that the vaccine was stored properly throughout its life. *The vaccine vial is empty* - The VVM symbol has **no relationship** to the vaccine volume or whether the vial contains vaccine. - An empty vial would be determined by **visual inspection** of the contents, not by interpreting the heat-sensitive VVM symbol.

Q: Which disease is prevented by giving a booster dose to a 5-6 year old child?

Diphtheria-Tetanus-Pertussis (DPT). **Explanation:** The correct answer is **Diphtheria-Tetanus-Pertussis (DPT)**. Under the National Immunization Schedule (NIS) in India, the **DPT 2nd Booster** is specifically administered at **5–6 years of age**. This dose is crucial because the immunity derived from the primary series (at 6, 10, and 14 weeks) and the 1st booster (at 16–24 months) begins to wane by school entry age. Providing this booster ensures robust protection against Diphtheria, Tetanus, and Pertussis during the early school years. **Analysis of Incorrect Options:** * **Measles (A):** Under the NIS, the first dose is given at 9 completed months and the second dose (as MR vaccine) at 16–24 months. There is no routine booster scheduled at 5–6 years. * **BCG (B):** This is administered at birth (or up to 1 year if missed). Repeat BCG or booster doses are not recommended by the WHO or the Government of India, regardless of Mantoux status. * **Diphtheria-Tetanus (DT) (C):** DT is used as a replacement for DPT only in children who have a contraindication to the Pertussis component (e.g., progressive neurological disorders). It is not the standard vaccine for the general population at this age. **High-Yield NEET-PG Pearls:** * **DPT vs. Td:** DPT is given up to 7 years of age. For children older than 7, the **Td (Tetanus and adult-dose Diphtheria)** vaccine is used because the full-strength Pertussis and Diphtheria components in DPT can cause severe local reactions in older children. * **School Entry Vaccine:** The 5–6 year DPT booster is often referred to as the "school entry" vaccine. * **Recent Change:** Note that the 10-year and 16-year doses, previously TT (Tetanus Toxoid), have now been replaced by **Td** to maintain diphtheria immunity in the population.

Q: Which vaccine in the Universal Immunization Programme (UIP) aims at preventing blindness?

Measles. **Explanation:** The correct answer is **Measles**. Measles is a leading cause of childhood blindness in developing countries. The virus causes severe depletion of Vitamin A levels in the body, which can lead to **xerophthalmia** (dry eyes), corneal ulceration, and eventually keratomalacia (softening of the cornea). Furthermore, measles infection can cause acute keratitis and secondary bacterial infections, exacerbating ocular damage. By preventing the infection through the Universal Immunization Programme (UIP), the risk of Vitamin A deficiency-related blindness is significantly reduced. **Analysis of Incorrect Options:** * **Rubella:** While Congenital Rubella Syndrome (CRS) can cause congenital cataracts and glaucoma, the primary public health goal of the Rubella vaccine in the UIP is the prevention of birth defects and fetal death, rather than the broad prevention of nutritional/infectious blindness in the general pediatric population. * **DPT (Diphtheria, Pertussis, Tetanus):** These vaccines prevent respiratory obstruction, severe cough, and neurological toxins; they have no direct clinical link to the prevention of blindness. * **Polio:** The Oral Polio Vaccine (OPV) and Inactivated Polio Vaccine (IPV) aim to prevent acute flaccid paralysis by targeting the anterior horn cells of the spinal cord; they do not affect ocular health. **High-Yield Clinical Pearls for NEET-PG:** * **Vitamin A Supplementation:** Under the UIP, the 1st dose of Vitamin A (1 lakh IU) is administered along with the Measles/MR vaccine at 9 months. * **Measles & Vitamin A:** Measles is the most common "precipitating factor" for nutritional blindness (Xerophthalmia) in children. * **WHO Recommendation:** All children diagnosed with measles should receive two doses of Vitamin A (24 hours apart) to prevent ocular complications and reduce mortality.

Q: To eradicate measles, what percentage of the population needs to be vaccinated?

95%. To achieve the eradication of measles, a herd immunity threshold of **95%** is required. This high threshold is dictated by the basic reproduction number ($R_0$) of the measles virus, which is one of the most contagious pathogens known to humans (each infected person can spread the virus to 12–18 susceptible individuals). ### Why 95% is Correct The formula for herd immunity threshold is $H = 1 - (1/R_0)$. Given that measles has an $R_0$ of 12–18, the mathematical requirement for stopping transmission is approximately 92–95%. Because the measles vaccine (Edmonston-Zagreb strain) is highly effective but not 100% protective in a single dose, a 95% coverage rate with two doses is the global standard set by the WHO to ensure the virus cannot find enough susceptible hosts to sustain an outbreak. ### Analysis of Incorrect Options * **70% (Option A):** This is the threshold for diseases with lower $R_0$ values, such as Diphtheria or Polio. * **80% (Option B):** This level of coverage may reduce the number of cases but is insufficient to prevent periodic outbreaks of measles. * **85% (Option C):** While this is the target for many routine immunizations, it falls short for measles, leading to "immunity gaps" that allow the virus to circulate. ### High-Yield NEET-PG Pearls * **Measles Eradication vs. Elimination:** Eradication is global; elimination is regional. India currently aims for Measles-Rubella (MR) elimination. * **Vaccine Type:** Live attenuated vaccine. * **Dose Schedule:** 1st dose at 9 completed months; 2nd dose at 16–24 months. * **Outbreak Definition:** Even a single laboratory-confirmed case of measles is considered an outbreak in a community. * **Vitamin A:** Administered alongside the vaccine to reduce morbidity and mortality.

Q: The 23-valent pneumococcal polysaccharide vaccine is recommended in all of the following conditions except?

Children less than 2 years of age. ### Explanation The **23-valent Pneumococcal Polysaccharide Vaccine (PPSV23)** contains purified capsular polysaccharides. The core immunological principle here is that polysaccharide antigens are **T-cell independent**. **1. Why Option C is correct:** In children **less than 2 years of age**, the immune system (specifically the splenic marginal zone) is immature and cannot mount an effective immune response to T-cell independent antigens. Therefore, PPSV23 is **ineffective and not recommended** in this age group. For children under 2, the **Pneumococcal Conjugate Vaccine (PCV)** is used instead, as it attaches the polysaccharide to a protein carrier, making it T-cell dependent and immunogenic in infants. **2. Analysis of Incorrect Options:** PPSV23 is indicated for "high-risk" individuals aged 2 years and older who are at increased risk of invasive pneumococcal disease (IPD): * **Option A (CSF Leak):** This is a high-risk condition as it provides a direct pathway for bacteria to cause meningitis. * **Option B (Chronic Cardiac Disease):** Conditions like congestive heart failure or cardiomyopathies increase vulnerability to severe pneumonia. * **Option D (Nephrotic Syndrome):** This is an immunocompromised state characterized by the loss of antibodies and complement factors in urine, significantly increasing the risk of pneumococcal infection. **High-Yield Clinical Pearls for NEET-PG:** * **PCV (e.g., PCV13):** Given in the National Immunization Schedule at 6 weeks, 14 weeks, and a booster at 9 months. * **PPSV23:** Does not produce mucosal immunity or herd immunity and does not induce immunological memory (unlike PCV). * **Sequential Vaccination:** In high-risk adults, PCV is often given first, followed by PPSV23 after an interval (usually 8 weeks to 1 year) to broaden serotype coverage. * **Asplenia/Sickle Cell Anemia:** These are the highest-yield indications for PPSV23 in patients >2 years old.

Question 1

Immunization with Rotavirus should be completed by what age?

Accepted Answer

12 months

Answer

2 months

Answer

3 months

Answer

18 months

Question 2

Peripheral health workers return one day late after an immunization session. The primary health centre is locked. The vaccine carrier still contains a few unopened vials of DPT vaccine and sufficient ice. What should the workers do?

Accepted Answer

Retain the vaccine in the ice box.

Answer

Return the vaccine vials to the refrigerator in the morning of the next day.

Answer

Get the health centre opened the same evening and keep the vaccine vials in the refrigerator.

Answer

Discard the vaccine vials.

Question 3

An 11-month-old child presents for vaccination. He has previously received Polio vaccine and BCG. What vaccines should be administered at this visit?

Accepted Answer

Measles, DPT, OPV, Hib, Hepatitis B

Answer

BCG, OPV, Hepatitis B

Answer

DPT, OPV, Hib, Hepatitis B

Answer

DPT, OPV, Hepatitis B

Question 4

An OPV vial shows a Vaccine Vial Monitor (VVM) in which the inner square is lighter than the outer circle. What does this symbol indicate?

Accepted Answer

Use the vaccine if the expiry date has not been reached

Answer

The vaccine has not been stored properly

Answer

The vaccine vial is empty

Answer

The vaccine has reached its expiry date

Question 5

DPT is contraindicated in which of the following conditions?

Accepted Answer

Progressive neurological illness

Answer

Family history of convulsions

Answer

Acute respiratory tract infection

Answer

Cerebral palsy

Question 6

Which disease is prevented by giving a booster dose to a 5-6 year old child?

Accepted Answer

Diphtheria-Tetanus-Pertussis (DPT)

Answer

Measles

Answer

BCG

Answer

Diphtheria-Tetanus (DT)

Question 7

Which vaccine in the Universal Immunization Programme (UIP) aims at preventing blindness?

Accepted Answer

Measles

Answer

Rubella

Answer

DPT

Answer

Polio

Question 8

To eradicate measles, what percentage of the population needs to be vaccinated?

Accepted Answer

95%

Answer

70%

Answer

80%

Answer

85%

Question 9

The 23-valent pneumococcal polysaccharide vaccine is recommended in all of the following conditions except?

Accepted Answer

Children less than 2 years of age

Answer

Cerebrospinal fluid leak

Answer

Chronic cardiac disease

Answer

Nephrotic syndrome

Question 10

Which of the following statements is true about the pneumococcal vaccine?

Accepted Answer

It is not given in splenectomy patients.

Answer

It is not given if the age is less than 2 years.

Answer

It is polyvalent.

Answer

It is derived from capsular protein.

Immunization and Vaccine-Preventable Diseases — MCQs

Immunization and Vaccine-Preventable Diseases — MCQs

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